Process for solvent refining hydrocarbon oils



Jan. 26, 1965 R, A. wooDLE PROCESS FOR SOLVENT REFINING HYDROCARBON OILSFiled July 18, 1961 v 2 Sheets-Sheet 1 Jan. 26, 1965 R. A. wooDLEPROCESS FOR soLvENT REFINING HYDRocARsoN ons 2 Sheets-Sheet 2 Filed July18, 1961 ein This invention is directed to a hydrocarbon treatmentprocess employing liquid-liquid solvent extraction. More particularly,it relates to a method of solvent refining hydrocarbons containing asmall portion of constituents co-boiling with the solvent. ln accordancewith the process of this invention, hydrocarbon oils containingconstituents co-boiling with the solvent are contacted with a solventforming separate extract and ratlinate phases. The extract phase or aportion thereof is distilled in the presence of a relatively highboiling hydrocarbon oil under extractive distillation conditionseffecting separation of solvent free of co-boiling hydrocarbons frombottoms comprising extracted oil in adrnixture with said relatively highboiling hydrocarbon oil. lailnate is disstilled in the presence of steamunder azeotropic distillation conditions to elfect separation of solventfrom refined oil. Extractive distillation bottoms are distilled in thepresence ofsteam under azeotropic distillation conditions to effectseparation of remaining solvent from the hydrocarbons or extractedhydrocarbons and remaining solvent from the relatively high boilinghydrocarbons.

In solvent refining processes wherein the solvent and material treatedhave substantially dierent boiling ranges, the solvent is readilyseparated from the extract and ramnate phases by simple distillation.However, separation by simple distillation is incomplete when the oiltreated contains components having true boiling points in the region ofthe boiling point or boiling range of the solvent. For example,hydrocarbon oils having initial boiling points by ASTM distillation ofless than about 625 F. may contain some components having true boilingpoints as low as about 325 F. Therefore, in treating hydrocarbon oilshaving initial boiling points by ASTM distillation less than about 625F. with furfural as a solvent, oils co-boiling with the furfural tend toaccumulate in the solvent thereby reducing its solvent power and itsselectivity for extraction. Heretofore, it has been proposed that theseco-boiling hydrocarbons be separated from solvents by azeotropicdistillation wherein a low boiling azeotrope of solvent and water isdistilled from the hydrocarbon. However, azeotropic distillation of theentire solvent stream circulated in the treating process requires aninordinately large amount of steam. Additionally, although azeotropicdistillation is effected at a temperature substantially below thetemperature of the boiling point of the pure solvent, substantialamounts of low boilingr hydrocarbons may be vaporized with the azeotropeparticularly when treating relatively low boiling stocks such askerosene, diesel fuel, and hydraulic oils.

ln `accordance with the process of this invention, extractivedistillation is combined with azeotropic distillation to eliect a highdegree of separation of co-boiling oils from solvent in a solventextraction process. The treating process of this invention is applicableto a Wide range of hydrocarbon oils, for example, it may be applied tothe manufacture of lrerosenes, diesel fuels, gasoil cracking stocks,light lubricating oil stocks, hydraulic oils, oils suited for thepreparation of specialty products, and oils suited for chemicalmanufacture. Although furfural is a preferred solvent useful in theprocess of this invention, other solvents may be employed which arepartially miscible with water at about 100 F. and

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which are capable of forming an azeotrope with water. Such solventsinclude for example, other furans, nitrobenzene, amines for example,aniline, ketones, for example 3-pentanone and mcsityl oxide, hydroxycompounds, for example phenol and n-amyl alcohol, aldehydes, forexample, benzaldehyde, nitriles, for example, propionitrile andbutyronitrile, and esters, for example n-butyl acetate and n-amylacetate. As is well known in the art, the solvent used may comprise amixture of several individual solvents and the solvent may be modir'iedby the inclusion of antisolvents, for example water.

in the extractive distillation step of this invention, distillativeseparation of solvent from dissolved hydrocarbons is effected in thepresence of a relatively high boiling hydrocarbon oil. The presence ofthe high boiling oil reduces the relative volatility of the co-boilingcomponents of the dissolved oil so that solvent free of coboilinghydrocarbons may be removed as distillate and all of the oil initiallydissolved in the solvent is removed as bottoms with the relatively highboiling oil. The extractive distillation is effected at a pressureselected to augment the effect of the high boiling oil on the relativevolatility of the co-boiling hydrocarbon and to achieve optimum and mosteconomical equipment design and operation. Preferred pressures in theextractive distillation step, depending upon the hydrocarbon oil feed,

- the solvent, and the relatively high boiling oil employed,

may be within the range of less than atmospheric, that is, a vacuum, upto about live atmospheres or higher.

The relatively high boiling oil itself should be free of componentsboiling in the region of the solvent and preferably should consist ofcomponents having true boiling points at least F. above the boilingrange of the solvent. In some cases, the relatively high boiling oil maybe used on a once through basis and 'discharged with the dissolved oilin which case the boiling ranges of the two oils may overlap. Generally,however, it is desirable to separate the dissolved oil as a separateproduct by distillation, in which case, the relatively high boiling ilshould consist of components boiling wholly above the treated oil.Suitable high boiling oils include both distillates and residua. Aparaflinic residium boiling wholly above 760 F. at atmospheric pressureis preferred for use as a relatively high boiling oil when treating oilsboiling within the range of about 350 to 700 F. by ASTM distillation.

lt is an object of this invention to provide a means of treatinghydrocarbon oils containing constituents coboiling with the solvent.Other objects Will be apparent from the following description andclaims. An advantage of the process of this invention is that the oilcontent of the solvent stream is maintained at a desirably low levelthereby maintaining high solvent efficiency. Another advantage of thisinvention is that the oil content of the circulating solvent ismaintained at a low level without requiring extremely high steamconsumption. Another advantage of this invention is that separation ofoil is effected without chilling or dilution and with a minimum ofreconcentration Kof the solvent.

FGURE l is a flow diagram of one form of the process of this inventionadapted primarily to the refining of relatively low boiling oils.

FIGURE 2 is a liow diagram of an embodiment of this invention in anapparatus useful for the solvent treatment of both light and heavyhydrocarbonv oils. Although the drawings illustrate arrangements ofapparatus in which the process of this invention may be practiced, it isnot intended to limit the invention to the particular apparatus ormaterials described.

Referring Ito FlGURE l, a light lubricating oil stock is charged throughline il to extraction tower 2. ln extraction tower 2, the oil iscountercurrently contacted with solvent introduced into the top of towerZ through line 3. The solvent may suitably be wet furfural, that is,liquid furtural containing a small amount of dissolved water.Raiinatemix, comprising'retined light lubricating oil stock and a smallamount of dissolved solvent is vwithdrawn through line 4 and passed torafnate stripper 7. Water in the form of steam is introduced at thebottom of stripper 7 through line 8 in an amount suiiicient to form anazeotrope with all of the Solvent contained in the rainate-mix therebyremoving all of the solvent in the azeotrope withdrawn as distillatethrough line 11i. Relined oil free of solvent is withdrawn from thebottom of stripper 7 through line 11.

The azeotropic mixture in line comprises vapors of solvent, water, and asmall amount of hydrocarbon oil. The vapor mixture is condensed incooler 15 and therresulting condensate is passed through line 16 toseparator 17. Three liquid phases separate, that is an oil phasecontaining a small amount of dissolved solvent and water, a water phasecontaining a small amount of dissolved solvent and oil, and a solventphase containing a small amount of water and oil. Separator 17 isprovided with internal batlles indicated by dotted lines 1S and 19 topermit separate withdrawal of the three phases. Separated solvent phaseis withdrawn through line 2@ and returned to extraction tower 2 throughline 3. arated water phase is withdrawn through line 21 for subsequentsolvent recovery. Separated oil phase is withdrawn through line 22,passed to washer 23 and countercurrently contacted with water thereinintroduced through line 24. Oil free of solvent is withdrawn throughline 25 and combined with the rened oil in line 11 to provide a solventreiined light lubricating oil stock product of the process. Waterwashings from washer 23 are withdrawn through line 26 and combinedSepwith the water phase in line 21 for subsequent solvent recovery. Y

Extract-mix comprising solvent and dissolved extracted oil is Withdrawnfrom the bottom of tower 2 through line 30. Extract-mix is cooled incooler 31 land the cooled stream is passed through line 32 to settler33. A secondary rarinate phase separates from the remaining extractmixin settler 33. This separated secondary ratinate contains a small amountof dissolved solvent and is withdrawn through line 36 and passed to washtower 37 where it is countercurrently contacted with water intro- -ducedthrough `line 33. Water washings are withdrawn through line 4t)for'subsequent solvent recovery. Washed secondary rainate is withdrawnthrough line 39 as a part ofV the extract product of the processdischarged through line 41.

Secondary extract-mix withdrawn from settler 33 through line is heatedin heater 46 and passed through line 47 to ash drum 48. In flash drum 43all of the solvent is vaporized together with a part of the extractedhydrocarbon oil and the resulting vapors are discharged through line 49to extractive distillation tower Sti. Stripped extract free of dissolvedsolvent is withdrawn from the bottom of tiash drum 4S through line 51 asa part of the extract product of the process discharged through line 41.

In extractive distillation tower 59, the hydrocarbon and solventYvaporsvare distilled in contact with a relat'ively high". boilinghydrocarbon oil introduced into the top of tower through line 5S. Bydistilling the solvent a-nd extract vapors in Contact with the highboiling oil, the extract vapors are condensed in the high boiling oiland solvent free of oil is removed as distillate through line 56. Theextractive distillation tower bottoms, comprising the high boiling oil,extract oil, and a part of the solvent, are withdrawn through line 57and passed to extract stripping tower 53.

Steam is introduced through line 59 into the bottom oftower 58 in anamount suicient to form the minimum boiling azeotrope with all of thesolvent in the stream charged to tower 5S. All of the solvent isdistilled overhead as azeotrope along with the extract oil. High boilingoil is withdrawn from the bottom of tower for recycle to extractivedistillation tower 5t) through line 55. Extract and azeotrope vaporsremoved as distillate from tower 5S are passed through line 65, coolerand line 67 to separator 6%. Separator 6d is provided with internalbattles indicated by dotted lines 69 and 7 ti to permit separation ofthe three liquid phases formed upon condensing the distillate from tower53. VOil phase containing a small arount of dissolved water and solventis withdrawn through line 72 and combined with the oil in line 36 forwater washing and recovery. Separated water phase is withdrawn throughline 71, combined with water streams in lines 21 and Alti and passed tofractionator 75 for recovery of dissolved solvent. Solvent phase iswithdrawn through line`76 and recycled with the extract-mix in line 32through the settler, flash drum and extractive distillation circuit.

Solvent vapors substantially free of oil in line 56 are condensed incooler 77 and passed through line. 7S to water-solvent separator 79.Water phase separating in separator 79 is withdrawn through line 30 andpassed to fractionator 75 for recovery of dissolved solvent. leparatedsolvent phase is passed through line S5 to accumulator Se from whichsolvent is withdrawn .through line 3 for charge to extraction tower 2.

Fractionator 75 is employed to recover solvent dissolved in water fromthe water discharged from the systent The Water streams charged throughlines 21, 4t) and 3?, contain dissolved solvent which is removed bydistilling the minimum boiling azeotrope overhead through line 87. Theazeotrope vapor stream is combined with the vapor stream in line 56 forcondensation, separation or solvent phase, and return to the extractionsystem. Water free of solvent is Withdrawn through line 8S for dischargefrom the system.

FGURE 2 illustrates a method of integrating the process of thisinvention into a system useful in the solvent refining of a full rangeof hydrocarbon oils including both oils containing solvent co-boilingcomponents and oils wholly boiling substantially above the boiling rangeof the solvent. In the rening of high boiling hydrocarbon oilscontaining no components boiling in the region of the boiling range ofthe solvent, charge oil is introduced through line 101 into tower 102and contacted countercurrently with solvent introduced through line 103.Raf. inate-mix withdrawn through line 105 is passed to rened oilstripper 1% where the solvent is removed by stripping with steamintroduced through line 1417. Azeotropic mixture of steam and solvent iswithdrawn through line 11@ for solvent recovery and reconcentration aswill be described hereinafter. Rened oil is Vwithdrawn through line 111.

Extract-mix is withdrawn through line and passed to solvent iiash tower121. The bulk of the solvent is removed as vapor free of oil throughline 122 and passed to solvent drying tower 131 described hereinafter.Flashed extract-mix containing a small amount of residual solvent ispassed through line 123 to stripper 124 wherein it is contacted withsteam introduced through line 127 to remove residual solvent. Anazeotropic mixture of solvent and water vapor is withdrawn through linefor reconcentration and recovery. Extract free of solvent is withdrawnthrough line 126.

Solvent is recovered and concentrated in a distillation systemcomprising solvent recovery tower 130 and solvent solvent drying tower131. In solvent drying tower 131, water is removedtrom the solvent bydistilling all of the water overhead as the low boiling azeotrope whichis discharged through line 31139 and combined with the azeotrope vaporsin line 132 for condensation and phase separation. Solvent free of wateris withdrawn from the bottom of tower 131 for recycle to extractiontower 102 through line .103.

Water phase from settler $5 is withdrawn through line 140 and passed tosolvent recovery tower 130. In solvent recovery tower 130, all of thesolvent is distilled overhead as the minimum boiling azeotrope which isdischarged through line 141 and combined with the azeotropic mixture inline 132 for condensation and phase separation. Water free of solvent isdischarged from the bottom of tower 13) through draw-oli line 141:1.

in reiining oils containing low boiling oils, both the raiiinate-mix inline 105 and the extract mix in line 120 may contain constituentsco-boiling with the solvent. Low boiling constituents in theraiiinate-mix appear in the distillate from refined oil stripper 106,along with the azeotropic mixture of steam and solvent. This vapormixture is withdrawn through line M and 11h11 to cooler 150. Condenseddistillate is passed through line il to separator l52 whe-rein oil,water and solvent phases are separated. Oil phase is withdrawn throughline 153 and passed to washer 155 wherein it is countercurrentlycontacted with water introduced through line 154. Light refined oil isdischarged through line H6 and may be combined with the refined oil fromline 111 as the reiined oil product of the process. Water washings arewithdrawn from the bottom of tower 155 through line 166, combined withwater phase withdrawn from separator 152, and the mixture passed throughline 161 to solvent recovery tower 130.

Extract-mix containing constituents co-boiling with the solvent iswithdrawn from tower 102 through line 125B and passed through line 12Wto extractive distillation tower lofi Relatively high boiling oil isintroduced to the top of tower 165 through line 166. Extract-mix isdistilled in tower 16S under conditions effecting removal of the bulk ofthe solvent as an overhead distillate substantially free of hydrocarbonoil. Solvent vapor is discharged through line 167 and combined with thestream passed through line 125 for solvent recovery and concentration.Extractive distillation tower bottoms comprising a relatively smallamount of solvent, the extract oil, and the relatively high boiling oilare withdrawn through line 170 and passed to tower 124.

Extractive distillation tower bottoms are distilled in tower i224 withsteam introduced through line 127 under conditions etiectingvaporization and distillation of remaining solvent and extract oil whichare discharged through lines 25 and 12551 to condenser 171. Condenseddistillate is discharged through line 172 to separator 1173. Oil, Waterand solvent phases are separated in separator 173. Oil phase iswithdrawn through line 175 to washer 176 wherein it is countercurrentlycontacted with water introduced through line 177. Extract product of theprocess is discharged through line 178. Water washings are withdrawnfrom the bottom of washer 176 through line 179, combined with waterphase withdrawn from separator 173 in line lh, and the mixture passed tosolvent recovery tower 130. Separated solvent phase is withdrawn fromseparator 173 through line 190 and returned to the feed to extractivedistillation tower in adniixture with the extract-mix in line 120g.

K Example The following example illustrates the application of theprocess of this invention to the reiining of a light lubricating oilstock useful in the manufacture of hydraulic oils. In the followingexample, ilow rates are expressed in terms of liquid barrels per hourregardless of whether the particular stream is in the liquid or vaporform. A lubricating oil charge stock having an ASTM distillation initialboiling point of 440 F., a 50 percent point of 490 F., and an endpointof 632 F. at a rate of 18.7 barrels per hour is countercurrentlycontacted with 49.4 barrels per hour of solvent having a composition of90 percent furfural, 9 percent water and 1 percent oil. Extraction iseected with a top tower temperature of 17l F. and a bottoni towertemperature of 122 F. Raiiinate-rnix at a rate of 15.3 barrels per houris steam stripped at a top tower temperature of 208 F. to produce 12.7barrels per hour of oil bottoms free of solvent and an overheadazeotropic distillate. The azeotropic distillate is condensed separating1.7 barrels per hour of solvent phase comprising '86 percent furfural, 3percent oil, and 1l percent water, 5.4 barrels of water phase comprising92 percent water and 8 percent furfural and .4 barrel or" oil phasecomprising percent oil, 18 percent furtural and 2 percent water. Thesolvent phase is returned as part of the solvent passed to theextraction tower, the water phase is directed to the solvent recoveryequipment, and the oil phase is water washed and combined with theraiinate stripper bottoms to produce 13.0 barrels per hour of reiinedoil product.

Extract-mix at a rate of 52.8 barrels per hour comprising 80 percentfurfural, l2 percent extract oil, and S percent' water together with 4.8barrels of recovered solvent as hereinafter provided comprising 75percent turtural, 15 percent oil, and 10 percent water are cooled to 105F. effecting separation of .5 barrel per hour ot secondary ratlinatewhich is water washed to provide a part of the extract product of theprocess. Remaining extract-mix is heated to 325 F. and dashed from aresidue of 0.8 barrel per hour of extract. Flashed vapors equivalent to56.2 barrels per hour are passed to an extractive distillation toweroperated at atmospheric pressure and a top tower temperature of 325 F. Aheavy paraliinic residual oil boiling wholly above 760 F. at atmosphericpressure is reiluxed to the top of the extractive distillation tower ata rate of 56.2 barrels per hour. Extractive distillation tower overheadat a rate of 46.2 barrels per hour comprising 89 percent furfural, 10percent water and 1 percent oil is condensed and passed to afurfural-water settler.

Extract distillation tower bottoms, at a rate ot 66.2 barreis per hourcomprising 8 percent extract, 7 percent furtural kand percent heavy oilis passed to an extract stripper. The extractive distillation towerbottoms are stripped with 12.7 barrels per hour or" steam at' a toptower temperature of 208 F. to separate 56.2 barrels per hour of heavyoil as bottoms for recycle to the extra/:tive distillation tower and22.7 barrels per hour of distillate. Distillate is condensed to formoil-rich, water-rich and turfural-rich phases. Furfural phase at a rateof 4.8 barrels per hour comprising 75 percent furfural, l5 percent oiland l0 percent water is withdrawn and adrnixed with the extract-mixpassed to the extractive distillation tower. Water at a rate of 13.2barrels per hour containing 8 percent turfural is passed to a water fromurfural fractionator for the recovery of furural. Oil phase at a rate of4.7 barrels per hour is withdrawn, water washed, and combined with thesecondary raffinate and the extract-mix ashed residue to produce 5.8barrels per hour of extract product.

l claim:

l. ln the solvent refining of a feed hydrocarbon oil containing at leasta small portion of constituents co-boiling with a liquid solvent whereinsaid feed hydrocarbon is contacted with said solvent in a solventrefining step forming separate extract and raiinate phases, said solventbeing at least partially miscible with water at F. and capable offorming an azeotrope with water, the improvement' which comprisesdistilling at least a portion of said extract phase in contact with arelatively high boiling hydrocarbon oil consisting of hydrocarbonshaving true boiling points at least 100 F. above the boiling range ofsaid solvent in an extractive distillation zone, withdrawing solventfree of co-boiling hydrocarbons as distillate from said extractivedistillation Zone for recycle to said solvent refining step, passingbottoms from said extractive distillation zone comprising saidrelatively high boiling hydrocarbon oil, constituents of said feedco-boiling with said solvent, and solvent to an azeotropic distillationzone, passing steam to said azeotropic distillation zone, withdrawingsaid relatively high boiling hydrocarbon oil as bottoms from saidazeotropic distillation zone for recycle to said extractive distillationzone, withdrawing ternary azeotrope comprising co-boiling oil, water,and solvent as distillate from said azeotropic distillation Zone,condensing said ternary azeotrope forming separate oil, water, andsolvent phases, said separate oil phase comprising hydrocarbonscoboiling with said solvent, withdrawing said separate oil phase,withdrawing said separate Water phase, recycling said separate solventphase to said extractive distillation Zone, and recovering refinedhydrocarbon oil from said ratiinate.

2. The process of claim l wherein said solvent cornprises furfural.

3. The process of claim 1 wherein said co-boiling hydrocarbons comprisehydrocarbons having true boiling points in the region of the solventboiling temperature and below.

4. The process of claim 1 wherein said extractive distillation isVeected at an absolute pressure less than about rive atmospheres.

5. The process of claim 1 wherein tillation is effected under vacuum.

6. In the solvent refining of a feed hydrocarbon oil containing at leasta small portion of constituents coboiling with a liquid solvent whereinsaid feed hydrocarbon is contacted with said solvent in a solventrefining step forming separate extract and raffinate phases, saidsolvent being at least partially miscible with water at 100 F. andcapable of forming an azeotrope with water, the improvement whichcomprises distilling at least a portion of said extract phase in contactwith a relatively high boiling hydrocarbon oil consisting ofhydrocarbons having true boiling points at least 100 F. above theboiling range of said solvent in an extractive distillation zone,withdrawing solvent free of co-boiling hydrocarbons as distillate fromsaid extractive distillation zone for recycle to said solvent refiningstep, passing bottoms from said extractive distillation zone comprisingsaid relatively said extractive dishigh boiling hydrocarbon oil,constituents of said feed co-boiling with said solvent, and solvent to afirst azeotropic distillation zone, passing steam to said firstazeotropic distillation zone, withdrawing said relatively high boilinghydrocarbon oil as bottoms from said first azeotropic distillation Zonefor recycle to said extractive distillation zone, withdrawing a firstternary azeotrope as distillate from said azeotropic distillation zone,condensing said first ternary azeotrope forming separate first oil,first water, and irst solvent phases, said first oil phase comprisinghydrocarbons co-boiling with said solvent, withdrawing said first oilphase, withdrawing said first water phase, recycling said iirst solventphase to said extractive distillation zone, passing said ratiinate phaseto a second azeotropic distillation zone, passing steam to said secondazeotropic distillation Zone, withdrawing refined hydrocarbon oil asbottoms from said second 'azeotropic distillation zone, withdrawing asecond ternary azeotrope as distillate from said second azeotropicdistillation zone, condensing said second ternary azeotrope formingseparate second solvent, second oil, and second water phases, recyclingsaid second solvent phase to said solvent refining step withdrawing saidsecond water phase, Water washing said second oil phase, and withdrawingthe water washed second oil phase.

7. The process of claim 1 wherein said extract phase is subjected topre-distillation prior to passing to said extractive distillation Zoneeffecting separation of a portion of the extracted hydrocarbon oil freeof solvent'.

References Cited in the file of this patent UNITED STATES PATENTS2,216,932 Atkins Oct. 8, 1940 2,361,493 Patterson Oct. 31, 19442,526,722 Beavon Oct. 24,1950 2,567,172 Arnold et al. Sept. 11, 19512,685,556 Hachmuth Aug. 3, 1954 2,745,790 Manley May 15, 1956 2,842,484Fleck July 8, 1958 2,908,731 Kohle Oct. 13, 1959 2,909,576 Penske et al.Oct. 20, 1959 2,936,283 Hutchings May 10, 1960 FOREIGN PATENTS 476,610Great Britain Dec. 13, 1937

1. IN THE SOLVENT REFINING OF A FEED HYDROCARBON OIL CONTAINING AT LEASTA SMALL PORITON OF CONSTITUENTS CO-BOILING WITH A LIQUID SOLVENT WHEREINSAID FEED HYDROCARBON IS CONTACTED WITH SAID SOLVENT IN A SOLVENTREFINING STEP FORMING SEPARATE EXTRACT AND RAFFINATE PHASES, SAIDSOLVENT BENING AT LEAST PARTIALLYU MISCIBLE WITH WATER AT 100*F. ANDCAPABLE OF FROMING AN AZEOTROPE WITH WATER, THE IMPROVEMENT WHICHCOMPRISES DISTILLING A TLEAST A PORTION OF SAID EXTRACT PHASE IN CONTACTWITH A RELATIVELY HIGH BOILING HYDROCARBON OIL CONSISTING OFHYDROCARBONS HAVING TRUE BOILING POINTS AT LEAST 100*F. ABOVE THEBOILING RANGE OF SAID SOLVENT IN AN EXTRACTIVE DISTILLATION ZONE,WITHDRAWING SOLVENT FREE OF CO-BOILING HYDROCARBONS AS DISTILLATE FROMSAID EXTRACTIVE DISTILLATION ZONE FOR RECYCLE TO SAID SOLVENT REFININGSTEP, PASSING BOTTOMS FROM SAID EXTRACTIVE DISTILLATION ZONE COMPRISINGSAID RELATIVELY HIGH BOILING HYDROCARBON OIL, CONSTITUENTS OF SAID FEEDCO-BOILING WITH SAID SOLVENT, AND SOLVENT TO AN AZEOTROPIC DISTILLATIONZONE, PASSING STEAM TO SAID AZEOTROPIC DISTILLATION ZONE, WITHDRAWINGSAID RELATIVELY HIGH BOILING HYDROCARBON OIL AS BOTTOMS FROM SAIDAZEOTROPIC DISTILLATION ZONE FOR RECYCLE TO SAID EXTRACTIVE DISTILLATIONZONE, WITHDRAWING TERNARY AZEOTROPE COMPRISING CO-BOILING OIL, WATER,AND SOLVENT AS DISTILLATE FROM SAID AZEOTROPIC DISTILLATION ZONE,CONDENSING SAID TERNARY AZEOTROPE FORMING SEPARATE OIL, WATER, ANDSOLVENT PHASES, SAID SEPARATE OIL PHASE COMPRISING HYDROCARBONSCOBOILING WITH SAID SOLVENT, WITHDRAWING SAID SEPARATE OIL PHASE,WITHDRAWING SAID SEPARATE WAER PHASE, RECYCLING SAID SEPARATE SOLVENTPHASE TO SAID EXTRACTIVE DISTILLATION ZONE, AND RECOVERING REFINEDHYDROCARBON OIL FROM SAID RAFFINATE.